Andrew jay cross



A. J. CROSS.

METHOD OF EDGE FUSING OPHTHALMIC LENS BLANKS.

APPLICATION FILED JUNE 28, 1921.

1,432,235. 'Patentd 0ct.17,1922'.

INVENTOR ATTOR N EY Patented Oct. 17, 1922.

ANDREW JAY CROSS,

PATENT orrica.

OF NEW YORK, N. Y.

METHOD OF EDGE-FUSING OPHTHALMIC-LENS BLANKS.

Application filed June 28,

To all whom it may concern:

Be it known that I, ANDREW JAY Cnoss, a citizen of the United States, and a resident of thecity, county, and State of New York, have invented a new and useful Im provement in thejMethod of Edge-Fusing Ophthalmic-Lens Blanks, of which the fol lowing is a full, clear, and exact description.

In the manufacture of multifocal ophthalmic lenses, it is a practice to unite the major and minor lens membersby fusing them together edge to edge, and usually with the major member slightly overhanging the inner surface of the minor member. In the manufacture of such lenses and blanks from which multifocal lenses are ground, it is essential that the lines of demarkation between the various lenticular surface areas be sharply defined-by having the edges of the counter-sinks show an approximately right angled union with the edge of the adjoining lenticular surface area, and to accomplish this with precision, it is necessary to finish .some of the surface areas before fusion takes place. A difficulty in this operation is that whenever a polished surface of a glass lens is submitted to too high a heat, it loses its brilliancy of polish, and becomes what is called burned, and imperfect vision will result if lenses are made with these burned areas. Edge fusing without burning is difficult too, because the major member of the lens is so much larger in mass, that a comparatively high heat is required to soften it so as to make a perfect union, and such a heat is likely to-be too high for the minor member, which is of less mass.

The object of my invention is to provide means for edge fusing these major and minor members, and to shield or protect the minor member, and theipoints near the junction of the'major and minor members, so that the parts to be united'can be readily softened and fused without the objectionable burning, and with a perfect union which leavesthe completedblank so that it can be readily and perfectly finished. This will be better understood fromthe description which follows.

Reference is to be had to the accompanying drawings forming a part of this specification, in which similar reference characters indicate corresponding parts in all the views.

Figure 1 is a plan view of a blank adapt 1921. Serial No. 480,991.

ed to form two major members of the lens,

and having a hole therethrough;

blank 10 having a central opening 11 therevthrough. The edge wall of this opening 11 is beveled as shown at 12 in Figure 3. In Figure 2 I show. the minor member 13, which is adapted to fit in the hole 11, and has a beveled edge 14: fitting the inner edge wall of the member 10. In practice the inner surface of the member 14 does not come quite flush with the inner surface of the major member 10, leaving the latter slightly overhanging as shown at a in Figure 3.

It is exceedingly difficult to accurately grind and polish the overhanging part a of the blank, and to facilitate the finishing of the lenses, it is customary to have the blank a of the major lens blank, or the innor surface of the member 13, finished and polished before fusing, and it is usually essential to have at least one of these surfaces so finished and polished. It will be seen at once that the mass of the part 10 is so much greater than that of the member 13, that if the parts are'heated in an oven so as to unite by fusion, such a temperature as is required to soften the larger member, is quite apt to burn or blur the inner surfaces of the member 14, and the part a of the larger member. This is a fact well understood by those skilled in the art.

I have found, however, that by partially insulating the inner portions of the major member, and also partially insulating the minor member 14, this difficulty can be obviated, the parts 10 and 13 will soften so as to cohere nicely, especially as-they should the parts are to be united, the member 13 is inserted in the hole 11 of the member 10, and they are placed on the bed 15 which should be of refractory material. and I have found carborundum best suited for the purpose. The top concave surface is shaped to fit the outer convex surfaces of the members 10 and 1 1, and is smoothly finished and polished so that it cannot injure the lens blanks. I then use an insulator for the inner parts of the lens members, which is preferaby formed as shown in Figure 3, in which a larger sheet of insulation 16 is adapted to cover and overlap the hole 11 of the major member, and this has preferably a reduced portion 16 adapted to lie within the inner portion of the hole 11, and close to but not quite touching the member 13. This insulation for the inner portions of the lens blank can be supported in any convenient way, and I have shown it supported by a light wire framework 18 attached to the bed 15. I preferably insulate the middle portion of the bed 15 on the under side by placing a strip of insulating material 17 thereon, and the bed can be countersunk slightly as shown in the drawing, so that the member 17 will fit in said countersunk portion.

The insulating parts placed opposite the major and minor lens portions to be united, should be of good heat insulating material, capable of withstanding the rather high temperature of the mufiiing furnace. I have found mica well suited for this purpose, as it protects the meeting and adjacent parts of the two lens members, withstands the heat perfectly, and can be conveniently shaped.

\Vhen the middle portions of the complete lens blank, that is of the members 10 and 13 and the parts adjacent to their union are protected and insulated as described, I get a perfect fusion of the parts, and no loss from burning. In carrying out the method, care should be taken to have the inner insulating member 1616 fit nicely into the opening 11 and overlap the adjacent parts of the member 10, but the insulation should not quite touch either member of the lens. The method can be carried out well without using the insulation 17, but I find it better to have this part also insulated.

Where the members of the lens blank are united by the method described, I have invariably succeeded in getting a perfect union, without injury to the joints or adjacent parts.

It will be understood, of course. that after the members 10' and 13 are united, the completed blank is cut in two transversely and finished in any usual or preferred manner to produce a pair of lenses, in which the parts of the member 1.3 correspond to the.

minor or close vision member of the lens, and the parts 10 to the distance or major portion of the lens.

The above example will show clearly how simple my method is, and how easily it can be carried into practice, but as already stated, I do not limit the invention to the particular forms shown or to the particular insulation, but claim broadly the step which includes the insulation of the parts to be united while they are subject to a temperature necessary for the purpose.

1. The herein described method of edge fusin glass lenses, which consists in subjecting the parts to be fused, while in position edge to edge, to a fusing temperature, and insulating the parts adjacent to the polnt of fusion so as to prevent excessive temperature at such point.

2. The herein described method of'edge fusing glass lens blanks, which consists in subjecting the parts to be united, while in position edge to edge, to a fusing temperature, and protecting the parts adjacent to the fusing point so that said parts shall not be subjected to injuriously high temperature.

3. The herein described method of edge fusing glass lens blanks, which consists in placing the members to be united 1n position edge to edge, subjecting the parts to be united to a fusing temperature, and covering the point of fusion and the adjacent parts with an insulating material so as to prevent the burning of said parts.

1. The herein described method of edge fusing glass lens blanks, which consists in subjecting the parts to be united to a fusing temperature while in position edge to edge, and shielding the parts at and near the point of union by an insulator placed opposite the point of union and adjacent parts, said insulator being held near said parts but out of contact therewith.

5. The herein described method of edge fusing glass lens blanks, which consists in placing the parts to be united on a bed with the edges to be united in contact, subjecting the united parts of the lens to a fusing temperature, and protecting the point of union and adjacent parts from too high temperature by placing insulators opposite said parts on the inner side of the lens members and on the under side of the bed.

6. A method of uniting glasslens blanks edge to edge by fusion, in which the meeting parts are protected substantially as herein shown and described.

ANDREW JAY GROSS.

WVitnesses:

VVARREN B. HUTOHINSON, M. G. O"DONNELL. 

